1. Field of the Invention
The present invention generally relates to deflection coils for cathode;ray tubes, and in particular, to an apparatus and a related method of forming gaps in a deflection coil.
2. Description of the Related Art
Cathode ray tubes (CRTs) are used in display devices to produce images. The basic elements of a CRT are a deflection yoke, one or more electron guns, and a phosphor screen. The deflection yoke converges and deflects electron beams emitted by the electron gun(s). In general, a deflection yoke include two pairs of coils, where the first coil pair (i.e., horizontal coil) deflects the electron beam in the horizontal direction and the second coil pair (i.e., vertical coil) deflects that same electron beam in the vertical direction.
One type of a deflection coil used in deflection yokes is a saddle-type deflection coil 100 as shown in FIG. 1. Typically, a coil-winding die and a winding machine are used to winding a conductive wire into a saddle-shaped coil. The conductive wire generally includes an insulation layer and an adhesive coating disposed about the insulation layer. After the conductive wire has been wound into a proper shape, the coil is heated to melt the adhesive coating and provide adhesive bonding between winding turns of the coil.
As the requirements of deflection yokes become more stringent, deflection coils take on more complicated and intricate winding patterns as shown in FIG. 2. The number, location and shape of the gaps in the deflection coil influence the magnetic field produced by the coil. One conventional method of forming gaps in a deflection coil requires the use of pin insertions in the die during winding. At various times during the winding process, the coil-winding die stops spinning momentarily to enable pins to be inserted in the winding area. After the pins have been inserted, the coil-winding die starts to spin again to wind the wire around the inserted pins. The pin insertions cause the path of the winding to change. By changing the path of the winding, gaps are formed between a previous winding path and a subsequent winding path. The timing of the pin insertions and the location of the pin inserting mechanisms incorporated into the coil-winding die dictate the location of gaps formed in a deflection coil. Gaps in a deflection coil produced by inserting pin mechanisms during a winding process are usually of a triangular or curved triangular shape, as shown in FIG. 2.
Such conventional method of forming gaps in a deflection coil during a winding process suffers from various disadvantages. For example, because pin inserting mechanisms are permanently incorporated into the coil-winding die and the winding machine, the pin inserting mechanisms increase the complexity of the die design and increase the cost of designing and producing the die and winding machine. Moreover, because pins are inserted during winding of the deflection coil, the coil-winding die must slow down or stop spinning momentarily to enable pins to be inserted during a winding process. As a result the winding process is slowed down and the production output rate is reduced. Furthermore, the shape, location, and number of gaps in the deflection coils are restricted to those already machined into the coil-winding die. In other words, if a design engineer decides to change the location of one or more gaps in a deflection coil, this would require making major design changes in the winding machine and the coil-winding die.
In accordance with one embodiment of the present invention, a method is provided for forming gaps into a saddle-shaped deflection coil subsequent to a winding process. The method includes winding a conductive wire into a saddle-shaped deflection coil using a winding machine and bonding the saddle-shaped deflection coil to provide adhesive bonding between winding turns of the coil while the coil remains in the winding machine. Then, the deflection coil is removed from the winding machine and heat is applied to the deflection coil after the deflection coil has been removed from the winding machine to a temperature above a first temperature and below a second temperature. Gaps are formed in the deflection coil subsequent to the winding process while the temperature of the coil is between the first and second temperatures.